Barley is a grain that has been a familiar part of the Japanese diet since ancient times in the form of cooked barley and rice, and the like. With the spread of polished rice and the Westernization of food, the consumption of barley has decreased. In recent years, it has accounted for only a small part of grain consumption. The annual per capital consumption of barley in Japan is 0.3 kg, as compared to about 60 kg for polished rice and 33 kg for wheat (Non-Patent Reference 1). Additionally, grains such as barley and oats contain relatively large amounts of β-glucans, a water-soluble dietary fiber, physiological functions of which have drawn considerable attention. β-Glucans are polysaccharides with 1-3 and 1-4 glucose bonds ((1-3), (1-4)-β-D-glucans). They are also the primary component of the walls of barley endosperm cells, constituting about 70 percent. There have been many reports of the health functions of β-glucans. For example, the US Food and Drug Administration (FDA) has allowed health claims that barley β-glucans have the effects of lowering serum cholesterol levels and reducing the risk of coronary heart disease (for example, Non-Patent Reference 2).
In Japan, as well, there have been reports that the dietary consumption of barley and oats lowers blood cholesterol (for example, Non-Patent References 3 and 4) and inhibits a rise in blood sugar level following a meal (for example, Non-Patent Reference 5). There have also been reports of various researches on dietary fiber and cancer prevention (for example, Non-Patent Reference 6).
As stated forth above, barley and oats are grains known to contain relatively large amounts of β-glucans. The content thereof is normally said to be about 3 to 6 mass % (for example, Non-Patent Reference 7). Accordingly, numerous methods of extracting β-glucans have been investigated. Examples are the method of production by aqueous extraction employing barley as a starting material (for example, Patent Reference 1), the method of obtaining β-glucans by alkali extraction, neutralization, and alcohol precipitation employing barley and oats as starting materials (for example, Patent Reference 2), the method of extracting β-glucans in 80° C. to 90° C. hot water (for example, Patent Reference 3), and the like. While not an extraction method, the method of raising the content of β-glucans in grain by milling and sifting grain has also been proposed (for example, Patent Reference 4).
However, the methods are basically methods of separating and concentrating β-glucans from grains such as barley. As set forth above, the quantity of β-glucans in grains such as barley is about 3 to 6 mass %. Compared to other components such as starches and proteins, this content is quite low. Accordingly, the residue following extraction is quite large relative to the β-glucan finished product, and must be used in low value-added products such as animal feeds or discarded as waste. Thus, the cost per unit of the product necessarily rises, restricting its use to certain supplements and in common foods, and rendering its widespread use problematic.
Thus, most of the methods that have been proposed thus far consist of concentrating the components of natural materials with health functions by extraction and separation for use in supplements and common foods. The artificial use of some of the components of natural materials and their use in medical treatment is effective in cases such as when it is necessary to control the intake of other natural components. However, such uses are not necessarily suitable in cases of consumption as common foods. For example, the good compositional balance of natural components ends up being compromised, harmful substances end up being unintentionally concentrated and accumulated, and large quantities of unused waste end up being produced as by-products. As a result, there tends to be a drawback in the form of high production costs.
There have also been efforts to popularize barley foods in which barley is utilized as is as a foodstuff (for example, Non-Patent Reference 7). However, the consumption of cooked barley and rice is limited. There is thus a need to develop various applied foods. When employed in applied foods, it is necessary to utilize not just polished barley grains, but to produce flour and formulate it into various food materials.
The milling of grains for use in foods has been a common practice since ancient times. Dietary fibers, including grain flours containing β-glucans, are commercially available. However, most of the β-glucan-containing grain flours thus far have had coarse particles, and most have lacked whiteness and been grayish-brown. There have been limits to the ability to provide foods that are both tasty and appealing in appearance.
Various methods of reducing the size of the particles of barley flour have been examined for such purposes. For example, the effects of different methods of milling on properties have been examined with the goal of developing a hulless barley flour that is suitable to processing (for example, Non-Patent References 8, 9, 10).
The development of types of barley that contain high contents of dietary fiber, particularly β-glucans 7 to 10% or more, through the improvement of barley varieties has been advancing (for example, Non-Patent Reference 13). The possibility of taking in quantities of β-glucans that are suited to the health without separating and concentrating β-glucans is increased by using these barley varieties with high β-glucan contents.